Re: [PATCH v2 10/11] arch/x86: Add AMD feature bit X86_FEATURE_MBA in cpuid bits array

From: Borislav Petkov
Date: Fri Oct 05 2018 - 17:31:22 EST


On Fri, Oct 05, 2018 at 08:56:09PM +0000, Moger, Babu wrote:
> From: Sherry Hurwitz <sherry.hurwitz@xxxxxxx>
>
> The feature bit X86_FEATURE_MBA is detected via CPUID leaf 0x80000008
> EBX Bit 06. This bit indicates the support of AMD's MBA feature.
>
> This feature is supported by both Intel and AMD. But they are detected
> different CPUID leaves.
>
> Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
> Signed-off-by: Sherry Hurwitz <sherry.hurwitz@xxxxxxx>

This SOB chain should be the other way around - first Sherry, then you.

> ---
> arch/x86/kernel/cpu/scattered.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
> index 772c219b6889..bd7853334b27 100644
> --- a/arch/x86/kernel/cpu/scattered.c
> +++ b/arch/x86/kernel/cpu/scattered.c
> @@ -17,7 +17,11 @@ struct cpuid_bit {
> u32 sub_leaf;
> };
>
> -/* Please keep the leaf sorted by cpuid_bit.level for faster search. */
> +/*
> + * Please keep the leaf sorted by cpuid_bit.level for faster search.
> + * X86_FEATURE_MBA supported by both Intel and AMD. But the cpuid
> + * levels are different. Add a separate enty for each.
> + */
> static const struct cpuid_bit cpuid_bits[] = {
> { X86_FEATURE_APERFMPERF, CPUID_ECX, 0, 0x00000006, 0 },
> { X86_FEATURE_EPB, CPUID_ECX, 3, 0x00000006, 0 },
> @@ -29,6 +33,7 @@ static const struct cpuid_bit cpuid_bits[] = {
> { X86_FEATURE_HW_PSTATE, CPUID_EDX, 7, 0x80000007, 0 },
> { X86_FEATURE_CPB, CPUID_EDX, 9, 0x80000007, 0 },
> { X86_FEATURE_PROC_FEEDBACK, CPUID_EDX, 11, 0x80000007, 0 },
> + { X86_FEATURE_MBA, CPUID_EBX, 6, 0x80000008, 0 },
> { X86_FEATURE_SME, CPUID_EAX, 0, 0x8000001f, 0 },
> { X86_FEATURE_SEV, CPUID_EAX, 1, 0x8000001f, 0 },
> { 0, 0, 0, 0, 0 }
> --

With that fixed:

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

--
Regards/Gruss,
Boris.

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